Caught short in a tourist hotspot? Instead of paying up to a pound to use a public loo or trying to sneak into the toilets at McDonald's, you can walk straight in to these convenient alternatives — and soak up a bit of culture on your way out...
Royal Festival Hall
Bypass the 50p-to-pee 'Jubiloo' by Jubilee Gardens and take your pick from the wealth of toilets in the Royal Festival Hall. Our tip? Take a ride in the singing lift — an installation by artist Martin Creed that does exactly what its unofficial name suggests — to one of the loos on the upper levels, where you'll rarely have to queue outside of performance times.
Further along the South Bank, you're spoilt for choice, with plenty of toilets in the BFI and National Theatre. At the BFI, the loos nearest the riverfront can get pretty busy — but continue past NFT2, turn left at the bottom of the stairs, and you'll find some much quieter toilets at the end of a corridor. Or head up to the mezzanine level, where there's always a fascinating film-related exhibition, and — whisper it — a rarely-occupied single toilet.
Head down to the basement at the Stables Market and follow the signs past a warren of stalls, including a brilliant second-hand booksellers. Don't be alarmed by the inevitable queue stretching out of the ladies': there are plenty of cubicles, so it shifts quickly. When you're done, have a browse at works by Banksy and co. in urban art gallery Accepted Rebellion.
Rich Mix, Shoreditch
A beigel's throw from Brick Lane on Bethnal Green Road, Rich Mix cinema and arts venue offers nice, clean, nearly-always-empty loos just inside the front door. It's also worth checking out the building's two exhibition spaces for small-but-perfectly-formed photography and art shows.
National Portrait Gallery
Since the Greater London Authority introduced a charge at the Trafalgar Square toilets in 2015, the National Gallery seems the obvious choice for a free pee in the area. Head round the corner to the National Portrait Gallery, though, and you'll find it far less crowded. The main loos are downstairs, next to the cloakroom. Even if you don't have time to linger, you can catch one of the gallery's small special displays.
Old Royal Naval College, Greenwich
It's 50p to use the public loos in Cutty Sark Gardens, but head into the Old Royal Naval College and you'll find free toilets next to the visitor centre. The centre's displays about Greenwich history are well worth a look, as is the adjoining Old Brewery with its Meantime beers (well, it would be rude not to — and at least you know where the loos are now.)
Bookshop loos are among our favourites — Foyle's on Charing Cross Road deserves a special mention, too — but many of them have taken the spoilsport stance of making their toilets accessible only via a door code printed on receipts from the in-store coffee shop. Not Waterstones on Piccadilly though. Here, there's a free toilet on every stairwell. Show your appreciation by buying a book on the way out.
Head home from Cannon Street and you can savour the experience of using the toilets at a mainline station without having to pay up to 50p and negotiate a tiresome two-way turnstile (Charing Cross, Victoria and London Bridge have also joined these prestigious ranks). The Cannon Street loos are downstairs next to the ticket office, along a series of clinical-looking corridors. Still got a few minutes before your train? Say hello to the Plumber's Apprentice, a 7ft sculpture by Martin Jennings on the concourse next to platform 4.
Victoria & Albert Museum
Give Harrods a wide berth and choose the V&A for your Knightsbridge comfort break. But don't make the rookie mistake of heading straight to the toilets nearest the main entrance: there's nearly always a long queue in the ladies', snaking down the stairs and obstructing the sinks. Go across the courtyard to the main café and turn right, then through the unassuming single doorway to the beautifully tiled restrooms. Do stop and admire the grand Gamble Dining Room before you leave.
White Cube Bermondsey
Can't find a loo between London Bridge and Tower Bridge? Head away from the river to White Cube on Bermondsey Street. Stride straight through the main doors of the gallery and down to the far end, where you'll find suitably swanky toilets to your right. Then take a slightly more sedate stroll through the exhibition spaces and bookshop on your way back.